A group pause needs three things, which are room to park a line of bikes, a flat place to sit and something nearby to eat, and the Sihlsee provides all three without fuss. The reservoir stretches east of Einsiedeln at about 889 metres, and its shores have wide verges, picnic areas and small beaches where a dozen riders can drop gear and take helmets off without blocking anyone. On warm days you will see families, anglers and paddlers, but the lake is big enough to absorb them.
Einsiedeln, three kilometres away, rewards a detour. The town is built around the Benedictine abbey, a huge baroque complex facing a wide curved square with a fountain in front. The church holds the Black Madonna, a medieval statue that has drawn pilgrims for centuries, and the abbey has long been a stop on the Way of St James through Switzerland. The monastery is also known for its stables, where it has bred Einsiedler horses for many generations. The main street leading to the square has cafés, bakeries and souvenir shops, and the pace of life is gentler than the traffic suggests.
The riding around the lake is easy. A road follows the north shore and another crosses the water on the bridge at Willerzell, with wide, flowing bends and a smooth surface. Traffic builds on summer weekends, with cyclists and day visitors, so groups should keep together and leave gaps for overtaking. In the early morning, mist often lies on the lake, and the first light on the Mythen peaks to the south is a worthwhile reward for an early start.
For fuel, Einsiedeln has several stations, and Feusisberg and Schindellegi, on the Zurich side, provide alternatives. There is a mix of lakeside restaurants and small kiosks, though they may be seasonal. If you are leading a group, a quick check of the opening hours in advance is a good idea, because Swiss places often close in the afternoon lull between lunch and dinner.
The lake is artificial and drops in winter, so the shoreline can look bare in spring. By midsummer it is full again, and the water is clean enough for a quick swim. Keep an eye on the weather, because storms form over the hills in the afternoon and can pass quickly.