The following things are what is considered in play:
~Active Pokemon, plus all cards attached
~Benched Pokemon, plus all cards attached
~A played Supporter card (when next to the Active Pokemon)
~Any Stadium card in play
The prizes, deck, discard pile, and hand are not considered in play.
When Sand Reset is used, what is reset is everything that is attached to a Pokemon. This includes Energy, Pokemon Tools, Technical Machines, and even stuff like Defender. It does not include the Pokemon or its pre-evolutions.
Please note, a Fossil card that is on the Bench is not shuffled, as it is treated as a Pokemon when in play.
Also, a card like Unown Q that is attached to a Pokemon will get shuffled, as it is treated as a Pokemon Tool and not a Pokemon.
And, of course, if Sand Reset gets Power Sprayed you can never use it again for that game (since Power Spray treats that Poke-Power as having been used).
edit: thank you penguin
