Apex Indoor option

[Xray]

Meat Eater (the one with the burpees, "2" I think) seems like a close substitute for an indoor Apex. Maybe increase the number of burpees or do them with max speed & effort.

[Corax]

I like ME II a lot, too. But for me, it''s nowhere near as challenging as my hill. Guess it depends how big of a hill you have to run;)

[J-Madd]

Try doing Meateater 2 for time, instead of the full one minute breaks. Yikes. That's my rainy day Apex, or what I go to when I need to give my joints a break from sprinting.