Can I store bike inside a regular tent?
The main difference is that the tent gives almost no protection against thieves, where a shed gives a little more protection as it is.
And a shed can be improved a lot with a simple anchor ring which you fix to the ground or through a wall so it is very hard to remove, and to which you lock your bikes.
A well set up tent of a decent quality will keep the rain off your bikes as good as a cheap shed roof, but most tents are not made to do their work months at a time and many will let water through the fabric in heavy or consistent rain, while most sheds, even cheap ones, do a better job to keep the rain out.
Depending on the climate you have where you are, you may find damp inside both the tent and the shed, or more in one than the other, in which case I would expect the tent to be less protection, as most of those are meant for short term use.
A hard layer under or in your tent or even using a tent without build in ground sheet and adding a ground sheet on a hard underlayer will improve against raising damp and keeping water on the ground away from your bike.
But again, a shed will do better and it will be easier to build it up so ground water and rainwater collected on the ground will be kept out.
And a tent which is build good enough to compete with a shed will cost the same as a shed.
For short time storage, like the bikes of visiting friends who are only there for a week at a time, a tent makes sense. But so would any roof, even without the build up sides of a shed, and a well build bike should not get damaged getting rained on, as long as it can dry off properly after a rain shower. Within a tent the bikes may stay damp longer, depending on how the climate is where you are.