Ahh, ok, I get it - you want white or nearly white fabric for covers and chairs and you have a whole stack of unwanted sheets etc that could be used, if only they were white !
Yes, any bleach will work, the thicker stuff will need to be diluted with some water and then the sheets soaked in it. Depending on what colour the sheets are now, you may need to bleach each sheet several times. The only time I've ever succeeded in totally removing the colour from anything was when I accidentally dripped thick bleach onto a dark coloured hand towel. When soaking the sheets, don't leave them in the bleach solution for too long or they will start to rot ! Just buy a large bottle of the cheapest bottle of thick bleach you can buy (Lidl or Aldi are about the cheapest supermarkets at the moment), then make up a bleach solution in a large container. I would use my bath or sink but only because they are a steel ones, I wouldn't do it in a plastic bath or sink. In a well ventilated room, try a solution of 10% bleach, 90% warm water, mix well, then using an old wooden spoon and wearing rubber gloves, gently add your sheet to the liquid and stir well. Leave for 5 minutes and check on what colour the sheet is, return to the solution if necessary for another 5 minutes. Make sure you rinse the sheet really well afterwards (I'd probably launder it and add some fabric conditioner once I was happy with the resultant colour). Let us know how you get on with one sheet before you do a whole stack of them !