bubble jet success depends on a chemical reaction between fabric, inkjet computer ink, and the bubble jet itself. there is also a recommended final rinse. this info is according to the store owner where i bought mine.
imho, if you used the sheets, which have already been chemically primed in some way, you would be breaking that 3-way link. also, bubble jet is costly. i would not waste it on a chancy effort like this.
why do you want to use the sheets? maybe you could save them for wallhangings that won't get washed often, if ever. bubble jet is made to be used on plain old cotton.