One of the best and easiest alpine excursions near Bend involves a jaunt to a glacial lake with no name perched inside a crater on Broken Top. There are a few ways to get here, and several longer route options, but my favorite is to ride a bike to the trailhead on the so-called "worst road in Oregon" and then descend back to town through Happy Valley and the awesome Bend MTB trail system.
Start near the Dutchman Flat Sno-Park across the highway from Mt. Bachelor. Then take either the Flagline Access Trail from the parking lot or ride up the highway to where the Metolius-Windigo Trail crosses. Both trails head up toward Happy Valley and Broken Top, passing Todd Lake along the way (Todd Lake is where you access the road by car).
The ride becomes increasingly scenic as you climb. Eventually the trail crosses the Middle Fork of Tumalo Creek in one of the few local bridge-less water crossings.
Soon after, you'll find a trail splitting off to the left toward that "worst road" (Forest Road 370, then 380). The best time to ride is when the road is still closed to car traffic in early to mid-summer so that there are fewer people out. Take the split off and ride up the road directly toward the jagged mountains in the background (Broken Top).
The road ends at the trailhead, which is where the Three Sisters Wilderness area begins. Thus, you must ditch your bike here for a bit and get to hiking.
From here it's just a few beautiful miles up toward the lake. Stop for ice-cold water and some awesome views back toward Mt. Bachelor along the way.
Eventually you'll climb the crest of a small crater and find this gem of a lake sitting on the other side. If you're like me, you will probably now have a warm beverage or two in your pack that needs cooling. It'll only take a couple minutes as this is some of the coldest water I've ever jumped into, especially early in the summer when the lake is still partially frozen.
Take a dip if you dare and enjoy yourself. If you want bigger views, continue on up the trail to the crest overlooking the lake. Otherwise, head back down to your bike and get excited for the rest of the ride. (If you've shuttled, you can ride all the way back down to town. Otherwise you'll head back to your car the same way you came.)
Once you get back to your bike, head back down to the Met-Win trail. If you're riding down to town, make a left and keep riding as you were before the turn off. Then you'll ride toward Happy Valley where the trail eventually passes the North Fork Trail (uphill biking only, so you have to pass it) and connects to upper Mrazek. From there you have a number of fun options including heading down Farewell to Tumalo Falls and the Tumalo Creek Trail or riding all the way down Mrazek either to Shevlin Park or the connector to Phil's Trailhead via a couple dirt logging roads.
See my Strava route here. For a longer ride consider biking up the North Fork Trail from near Tumalo Falls. And if you want to get some fishing in, pop over to Todd Lake and leave your bike at the trailhead before hiking 5-minutes up to the lake. Check out Bendtrails.org for a terrific map and more info on the MTB trails. Also, see more info on No Name Lake and the hiking options here. Always practice Leave No Trace ethics.