You can use sqlcmd
and put it in a batch to spawn 100 parallel processes. As an alternative you can use LinqPad
and a simple C# script that uses Tasks
and, too, spawns 100 processes.
If you want to have a parallel stored procedure execution, then you need to setup service broker
and a queue with the length of 100, but you won't be having exactly 100 parallel activations at once because service broker
adds workers as workload increases, so it won't happen instantaneously.