As has been reported here before, any foreign national from a Red Zone country (Israel, UK, USA) entering Ukraine must go into 14-day quarantine and can get out of quarantine by taking a COVID test in Ukraine. If you get a negative result then you can leave quarantine and move around freely.
Reports from Ukraine today show that they have adopted a new policy that eases this restriction for people coming from Red Zone countries. A foreign citizen who presents a negative test result from within 48 hours before entering Ukraine will be able to enter the country without the obligation of quarantine. You will not need to take another test in Ukraine as long as you show results from your country. The new regulations will take effect from August 1 and we will update here on the exact details when we know them.