#include <sourcemod>
#include <clientprefs>

Cookie g_hTestCookie;

public void OnPluginStart() {
	RegAdminCmd("sm_testcookie", cmdTestCookie, ADMFLAG_ROOT);

	g_hTestCookie = new Cookie("TestCookie", "", CookieAccess_Private);
}

public Action cmdTestCookie(int client, int args) {
	if (!client) {
		return Plugin_Handled;
	}

	Cookie testcookie = Cookie.Find("TestCookie");
	PrintToChat(client, "%sFound", testcookie == null ? "Not " : "");
	delete testcookie;

	g_hTestCookie.Set(client, "TestValue");
	CreateTimer(5.0, timerCookie, GetClientUserId(client));
	return Plugin_Handled;
}

Action timerCookie(Handle timer, int userid) {
	int client = GetClientOfUserId(userid);
	if (!client) {
		return Plugin_Continue;
	}

	char buffer[10];
	g_hTestCookie.Get(client, buffer, sizeof(buffer));

	PrintToChat(client, "Result: %s", buffer);
	PrintToChat(client, "Time: %i", g_hTestCookie.GetClientTime(client));
	PrintToChat(client, "Level: %i", g_hTestCookie.AccessLevel);
	return Plugin_Continue;
}

Found
Result: TestValue
Time: 1559265624
Level: 2